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Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm−1 region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined.
We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed
in these distances is an indication of the substitution effect.
It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the
case of o-disubstituted benzenes it is only 80% of the para-substituted shift. 相似文献
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With the advent of medium and large gamma detector arrays, it is now possible to look at nuclear structure at high rotational
forces. The role of pairing correlations and their eventual breakdown, along with the shell effects have showed us the interesting
physics for nuclei at high spins — superdeformation, shape co-existence, yrast traps, alignments and their dramatic effects
on nuclear structure and so on. Nuclear structure studies have recently become even more exciting, due to efforts and possibilities
to reach nuclei far off from the stability valley. Coupling of gamma ray arrays with ‘filters’, like neutron wall, charged
particle detector array, gamma ray total energy and multiplicity castles, conversion electron spectrometers etc gives a great
handle to study nuclei produced online with ‘low’ cross-sections. Recently we studied, nuclei in mass region 80 using an array
of 8 germanium detectors in conjunction with the recoil mass analyser, HIRA at the Nuclear Science Centre and, most unexpectedly
came across the phenomenon of identical bands, with two quasi-particle difference. The discovery of magnetic rotation is another
highlight. Our study of light In nucleus, 107In brought us face to face with the ‘dipole’ bands. I plan to discuss some of
these aspects. There is also an immensely important development — that of the ‘radioactive ion beams’. The availability of
RIB, will probably very dramatically influence our ‘conventional’ concept of nuclear structure. The exotic shapes of these
exotic nuclei and some of their expected properties will also be touched upon. 相似文献
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S. B. Chernyshuk B. I. Lev H. Yokoyama 《Journal of Experimental and Theoretical Physics》2001,93(4):760-770
We studied the collective elastic interaction in a system of many macroparticles embedded in a nematic liquid crystal. A theoretical approach to the interaction of macroparticles via deformation of the director field [1] is developed. It is found that the director field distortion induced by many particles leads to the screening of the elastic pair interaction potential. This screening strongly depends on the shape of the embedded particles: it exists for anisotropic particles and is absent for spherical ones. Our results are valid for the homeotropic and the planar anchoring on the particle surface and for different Frank constants. We apply our results to cylindrical particles in a nematic liquid crystal. In a system of magnetic cylindrical grains suspended in a nematic liquid crystal, the external magnetic field perpendicular to the grain orientation results in inclining the grains to the director and induces an elastic Yukawa-law attraction between the grains. The appearance of this elastic attraction can explain the cellular texture in magnetically doped liquid crystals in the presence of the magnetic field [2]. 相似文献
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Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
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Magnetic-field-induced mutual transformations of a hexagonal structure into linear chains were experimentally observed in a system of glycerol droplets freely suspended in the layer of a nematic liquid crystal with hybrid orientation. A qualitative explanation is suggested for the observed effect. 相似文献
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ABSTRACTIn this short review we summarise already published results to manifest very important role of high order elastic terms in the formation of colloidal structures in nematic liquid crystals (NLC). We reveal that every colloidal particle in nematics can be effectively represented as a triad of nonzero elastic moments. Usually colloidal particles in NLCs are treated with their elastic dipole and/or quadrupole moments only. But we demonstrate that octupole, hexadecapole and even 64-pole moments play an important role as well and determine parameters of different 1D, 2D and even 3D colloidal crystals in NLCs. In general the triad of the first three nonzero elastic moments can describe almost all colloidal structures observed so far. Dipole particles should be considered as hard spheroids with a triad of the dipole, quadrupole and octupole moments. Quadrupole particles should be treated as hard spheres with a triad of quadrupole, hexadecapole and 64-pole elastic momentsPACS numbers: 61.30.Dk, 82.70.Dd, 64.70.M? 相似文献
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Lev B Nych A Ognysta U Chernyshuk SB Nazarenko V Skarabot M Poberaj I Babic D Osterman N Musevic I 《The European physical journal. E, Soft matter》2006,20(2):215-219
The interaction between a colloidal particle and a focused laser beam in a nematic liquid crystal reveals an unusual anisotropic
Coulomb-like character. Experiments demonstrate two opposite directions in which the particle is attracted to and repelled
from the nematic region deformed by the light-induced director reorientation. In this work we present analytical analysis
of such behavior and derive the energy of interaction between colloidal particle and deformed director field. The analytical
solution is in good agreement with recent results obtained by computer simulation. 相似文献